Response pattern control in spite of failed array elements

Large arrays of many elements usually are shaded to achieve low sidelobes. However, in practice these arrays typically operate with some element failures that significantly degrade sidelobe performance. First, the effects of different numbers of failed elements on sidelobe levels are analyzed and illustrated with simulations. Statistics and bounds for sidelobe levels with failed elements are presented. The inability and limitations of conventional shading modifications to compensate for failed elements is discussed and illustrated. Missing elements give rise to large inter‐element spacings that in turn result in grating effects that cannot be compensated for using modified shading weights. An adaptive compensation approach for failed elements is then presented. This involves narrowband interpolation from nearby elements to estimate the missing data prior to applying the original shading weights. Failures of both isolated and neighboring elements are considered. When there is a strong source present it is relatively easy to estimate its value on missing elements. But this is exactly the case of interest, when sidelobe levels are important. The adaptive interpolation approach provides good bearing response patterns so that strong signals are well isolated in bearing. Results are illustrated with large array simulations with different failure patterns and multiple strong sources.